<template>
  <div class="pagination">
    <button :disabled="pageNo===1" @click="$emit('getPageNo',parseInt(pageNo - 1))">上一页</button>
    <!-- 前面 -->
    <button :class="{'active':pageNo===1}" v-if="startNumAndEndNum.start > 1" @click="$emit('getPageNo',1)">1</button>
    <button v-if="startNumAndEndNum.start > 2">···</button>

    <!-- 中间 -->
    <button :class="{active:page===pageNo }" v-for="(page,index) in startNumAndEndNum.end" :key="index" v-if="page >= startNumAndEndNum.start" @click="$emit('getPageNo',page)" >{{ page }}</button>

    <!-- 下面 -->
    <button v-if="startNumAndEndNum.end < totalPage - 1 ">···</button>
    <button v-if="startNumAndEndNum.end < totalPage " @click="$emit('getPageNo',totalPage)">{{ totalPage }}</button>
    <button :disabled="pageNo===totalPage" @click="$emit('getPageNo',parseInt(pageNo + 1))">下一页</button>
    <button style="margin-left: 30px">共 {{ total }} 条</button>
    <!-- <div >{{startNumAndEndNum.start}} ----{{ pageNo }}----- {{ startNumAndEndNum.end }} </div> -->
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props:["pageNo","pageSize","continues","total"],
  computed:{
    // 计算一共多少页面
    totalPage(){
      return Math.ceil(this.total / this.pageSize)
    },
    // 连续页码数至少5页
    startNumAndEndNum(){
      let start = 0, end = 0
      let {pageNo,continues,totalPage} = this
      
      // 不正常现象 continues（分页数） 已经大于了 totalPage（总页数）
      if(continues > totalPage){
        start = 1
        end = totalPage // 此时 end 直接等于 totalPage（总页数）
      }else{
        // 正常现象 continues（分页数） 一定是大于 totalPage（总页数）
        // 解决问题 如果 continues 数量为  7 则 pageNo - 3 为 5 则 pageNo - 3
        start = pageNo - parseInt(continues / 2)
        end = pageNo + parseInt(continues / 2)
        // 当起始值小于 1 或 2 时
        if(start < 1){
          start = 1
          end = continues // 5
        }
        // 当最后的值小于 大于 totalPage（总页数）
        if(end >= totalPage){
          end = totalPage
          start = (totalPage - continues) + 1
        }
      }
      
      return {start,end}
    }
  }
};
</script>

<style lang="less" scoped>

.pagination {
  text-align: center;
  .active{
    background: #409eff !important;
  }
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>